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Flow cytometry can also be used to demonstrate abnormalities in genetic material, but it cannot demonstrate which chromosomes are involved. Here is a large aneuploid peak next to a diploid peak in a fetus with triploidy (69, XXY). The large peak is due to the fact that the cell population from the fetus contains three sets of chromosomes. The diploid peak comes from maternal cells (the tissue sample used was placenta

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Triploidy occurs when there is double fertilization of an ovum (dispermy). The result may be 69, XXX or 69, XXY or 69, XYY. The extra set of paternal chromosomes predisposes to formation of a partial mole, features of which may or may not be grossly or microscopically apparent.

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One characteristic feature of triploidy is syndactyly involving the third and fourth digits of the fetal hand as shown here.

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